I've long since taken to carrying a USB battery that can charge and provide power at the same time. It's more reliable for me than USB condoms, and, well, it's a battery, which is useful too.

That’s not been my experience, but I’m sure it’s hyper location/company specific.

As another commenter mentioned, I too carry a battery for longer trips, which is useful for charging devices when physically on the move and away from outlets. The model I chose from Anker can also top up a MBP, albeit slowly.